Anaesthesia
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This narrative review discusses recent evidence surrounding the use of regional anaesthesia in the obstetric setting, including intrapartum techniques for labour and operative vaginal delivery, and caesarean delivery. Pudendal nerve blockade, ideally administered by an obstetrician, should be considered for operative vaginal delivery if neuraxial analgesia is contraindicated. Regional techniques are increasingly utilised in clinical practice for caesarean delivery to minimise opioid consumption, reduce pain, improve postpartum recovery and facilitate earlier discharge as part of enhanced recovery protocols. ⋯ Transversus abdominis plane blockade, wound catheter insertion and single shot wound infiltration are all effective techniques for reducing postoperative opioid consumption, with transversus abdominis plane blockade favoured, followed by wound catheters and then wound infiltration. Ilio-inguinal and iliohypogastric, erector spinae plane and rectus sheath blockade all require further studies to determine their efficacy for caesarean delivery in the presence or absence of long-acting neuraxial opioids. Future studies are needed to: compare approaches for individual techniques; determine which combinations of techniques and dosing regimens result in optimal analgesic and recovery outcomes following delivery; and elucidate the populations that benefit most from regional anaesthesia in the obstetric setting.
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Review
The role of peripheral nerve stimulation in the era of ultrasound-guided regional anaesthesia.
With the widespread use of ultrasound for localising nerves during peripheral nerve blockade, the value of electrical nerve stimulation of evoked motor responses has been questioned. Studies continue to show that, compared with nerve stimulation, ultrasound guidance alone leads to: significantly improved block success; decreased need for rescue analgesia; decreased procedural pain; and lower rates of vascular puncture. Nerve stimulation combined with ultrasound does also not appear to improve block success rates, apart from those blocks where the nerves are challenging to view, such as the obturator nerve. ⋯ Nerve stimulation can serve as a monitor against needle-nerve contact and may be useful in avoiding nerves that are in the needle trajectory during specific ultrasound guided techniques. Nerve stimulation is also a useful adjunct in teaching novices ultrasound-guided regional anaesthesia, especially when the position and or appearance of nerves may be variable. In this review, the changing role of nerve stimulation in contemporary regional anaesthetic practice is presented and discussed.
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The accuracy and reliability of ultrasound are still insufficient to guarantee complete and safe nerve block for all patients. Injection of local anaesthetic close to, but not touching, the nerve is key to outcomes, but the exact relationship between the needle tip and nerve epineurium is difficult to evaluate, even with ultrasound. Ultrasound has insufficient resolution, tissues are difficult to discern due to acoustic impedance and needles are more difficult to see with increased angulation. ⋯ Micro-ultrasound at the tip of the needle is in development. Early images using 40MHz in anaesthetised pigs reveal muscle striation, distinct epineurium and 30-40 fascicles > 75 micron in diameter. The next few years will see a technological revolution in tip-tracking technology that has the potential to improve patient safety and, in doing so, change practice.